JP6554149B2 - Sulfur-doped oxide solid electrolyte powder and solid battery containing the same - Google Patents

Description

  This application is based on and claims priority from Taiwan Patent Application No. 105124401, filed on August 2, 2016, the disclosure of which is incorporated herein by reference in its entirety. .

  The present invention relates to a sulfur-doped oxide solid electrolyte powder and a solid battery including the same.

  Currently, most industrial lithium batteries use organic electrolytes. However, due to safety issues with this type of battery, the development of solid electrolyte materials is urgent. After the conventional electrolyte was replaced with a solid electrolyte, the structural design of the battery became more flexible. The energy density can be effectively improved to meet the demand for lithium battery energy density in the market. However, the migration rate of lithium ions in the solid electrolyte cannot be further improved due to the restriction of grain boundary blockage. As a result, the lithium ion conductivity of the solid electrolyte is low and cannot meet the actual requirements.

  Therefore, a solid electrolyte having improved lithium ion conductivity is needed as a solid electrolyte that can be used in practical applications.

  One embodiment of the present invention is a sulfur-doped oxide solid electrolyte powder, wherein the amount of sulfur is 1 wt% to 5 wt% based on the weight of the oxide solid electrolyte powder. provide.

  Another embodiment of the present invention is a solid battery comprising a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein the solid electrolyte layer is the aforementioned sulfur-doped oxidized A solid battery containing the solid electrolyte powder is provided.

  The detailed description is described in the following embodiments with reference to the accompanying drawings.

  The present invention may be more fully understood by the following detailed description and examples made with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view of a solid state battery according to an exemplary embodiment of the present invention. FIG. 1 is a schematic view of a test unit for alternating current (AC) impedance analysis.

  The following disclosure provides many different embodiments or examples to implement various technical features of the provided subject matter. In order to simplify the present disclosure, specific examples of elements and arrangements are described below. These are, of course, for illustrative purposes only and are not intended to be limiting. For example, the formation of the first feature on or above the second feature in the following disclosure includes embodiments in which the first and second features are formed to be in direct contact with each other. Well, and also, additional features may be formed between the first and second features to include embodiments where the first and second features do not have to be in direct contact. Further, in this disclosure, reference signs and / or lexical terms may be repeated in various embodiments. This repetition is for the sake of brevity and clarity and as such does not define the relationship between the various embodiments and / or configurations described.

  In one embodiment, the present invention provides a sulfur-doped oxide solid electrolyte powder. In some embodiments, the sulfur may be elemental sulfur (S) and may be distributed in the crystals of the oxide solid electrolyte. In some embodiments, the oxide solid electrolyte comprises lithium lanthanum titanium oxide (LLTO). Since the radius of elemental sulfur and the radius of oxygen are similar, sulfur added in the oxide solid electrolyte can be partially replaced with oxygen to form a sulfur-doped oxide solid electrolyte.

  In one embodiment, the amount of sulfur in the sulfur-doped oxide solid electrolyte powder provided by the present invention may be 1 wt% to 5 wt% based on the weight of the oxide solid charge quality powder. It should be noted that a sulfur-doped oxide solid electrolyte powder formed with sulfur in an amount of 1 wt% to 5 wt% may have good lithium ion conductivity. This result may be related to the lattice constant of the oxide solid electrolyte. When the oxide solid electrolyte is doped with an appropriate amount of sulfur, the lattice constant of the oxide solid electrolyte changes, thereby increasing the diffusion rate of lithium ions in the oxide solid electrolyte and oxidizing The lithium ion conductivity of the solid electrolyte is improved.

  Conversely, if the amount of sulfur is too low (i.e. less than 1 wt%), the amount of sulfur may not be sufficient to change the lattice constant of the oxide solid electrolyte. Therefore, the movement rate and lithium ion conductivity of lithium ions in the grain boundaries cannot be increased. If the amount of sulfur is too high (i.e. higher than 5 wt%), other crystal structures may appear, which impede the migration path of lithium ions in the grain boundaries of the oxide solid electrolyte, and , Can reduce the moving speed.

In some embodiments, to form the sulfur-doped oxide solid electrolyte of the present invention, a solid sintering method can be used to dope elemental sulfur into the oxide solid electrolyte. Specifically, raw materials can be prepared according to chemical dosages and added to the designed amount of elemental sulfur. Depending on the various oxide solid electrolytes, the selection of raw materials can be adjusted according to requirements. For example, when the oxide solid electrolyte is lithium lanthanum titanium oxide (LLTO), the raw materials are lithium carbonate (Li ₂ CO ₃ ), lanthanum hydroxide (La (OH) ₃ ), and titanium dioxide (TiO ₂ ) possible. After water is added to the aforementioned raw materials, a mechanical attrition method can be used to uniformly mix all the raw materials in order to obtain a precursor that is a slurry. Examples of the mechanical grinding method include a ball grinding method, a vibration grinding method, a turbine grinding method, a mechanical melting method, and a plate-type grinding method. type grinding) or other suitable grinding method. The aforementioned precursor that is a slurry is then dried to obtain a precursor that is a dry powder. Note that if the high temperature sintering process is applied directly to the precursor of elemental sulfur-containing powder with elemental sulfur at atmospheric pressure, SO ₂ may be produced and that loss of sulfur may occur. It should be. Thus, in one embodiment of the present invention, a precursor that is a dry powder containing elemental sulfur is first subjected to a mixed gas of hydrogen and argon, under a protective atmosphere such as nitrogen or argon, and at At a temperature of 900 ° C., a presintering process is applied. Elemental sulfur is doped into the oxide solid electrolyte crystals during the pre-sintering process. A solid sintering process is then applied to the presintered powder at normal pressure and at a temperature of 1000 ° C. to 1300 ° C. to obtain a sulfur-doped oxide solid electrolyte powder. At this time, the solid-sintered powder forms a perovskite crystal phase, thereby obtaining the sulfur-doped oxide solid electrolyte powder of the present invention. However, depending on the requirements in its use, the resulting solid electrolyte powder may be further ground to obtain the desired particle size.

  In one embodiment, the present invention also provides a solid state battery 100 comprising a positive electrode layer 102, a negative electrode layer 104, and a solid electrolyte layer 106 disposed between the positive electrode layer and the negative electrode layer, as shown in FIG. Do. In some embodiments, the positive electrode layer 102 may include a known positive electrode active material used in solid state batteries. For example, a lithium-containing oxide or the like. In some embodiments, the negative electrode layer 104 may include a known negative electrode active material used in solid state batteries. For example, a carbon active material, an oxide active material, or a metal active material such as a lithium-containing metal active material. In some embodiments, the solid electrolyte layer 106 includes the aforementioned sulfur-doped oxide solid electrolyte powder, which moves carriers (eg, lithium ions, etc.) between the positive electrode layer 102 and the negative electrode layer 104. Act as an intermediary for In other embodiments, the solid electrolyte layer 106 may further include an adhesive such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), or polyoxyethylene (PEO), polyphenylene oxide (PPO) or An organic solid electrolyte such as polysiloxane may be included. The organic / inorganic composite solid electrolyte is formed by mixing an adhesive or organic solid electrolyte with the aforementioned sulfur-doped oxide solid electrolyte powder. In some embodiments, at least one of the positive electrode layer 102 and the negative electrode layer 104 can include the aforementioned sulfur-doped oxide solid electrolyte powder. The organic / inorganic composite solid electrolyte described above may be coated on the positive electrode layer 102 or the negative electrode layer 104 so as to form a coating layer. Thereafter, the negative electrode layer 104 or the positive electrode layer 102 is laminated on the coating layer and fixed by applying pressure along the lamination direction.

  As is known in the art, in addition, as shown in FIG. 1, the solid state battery may further include a positive electrode current collector 108 and a negative electrode current collector 110. The material, thickness, shape, and the like of the positive electrode current collector 108 and the negative electrode current collector 110 can be selected according to a desired application. Other detailed manufacturing processes for solid state batteries are known in the art and, therefore, will not be repeated to avoid unnecessary repetition. It should be noted that these embodiments are for illustrative purposes only and the scope of the invention is not limited thereto.

  The sulfur-doped oxide solid electrolyte powder provided by the present invention is currently most used, using a liquid electrolyte as a mediator to move the carrier between the positive electrode layer and the negative electrode layer of the lithium battery. It can replace the separator and electrolyte in lithium batteries. By doping with elemental sulfur, the present invention increases the migration rate of lithium ions in the oxide solid electrolyte and improves the lithium ion conductivity. Thereby, a solid electrolyte can be practically used.

  In order to illustrate the sulfur-doped oxide solid electrolyte powder provided by the present invention and its properties, examples and comparative examples are described below.

Preparation of oxide solid electrolyte [Example 1] Lithium lanthanum titanium oxide (LLTO) ... Sulfur amount 2.4 wt%
Lithium carbonate _{(Li 2 CO 3; Alfa Aesar} ) 18.2g, hydroxyl lanthanum (l anthanum hydroxide (La (OH ) 3); Alfa Aesar) 127.9g, and titanium dioxide _{(titanium dioxide (TiO 2);} Evonik 105.5 g of Industries) was mixed with 5.2 g of elemental sulfur (S; Showa Chemical Industry Co., Ltd.). 500 g of water was added to the mixture and then ground for 24 hours by the ball mill method. After all the raw materials were uniformly mixed, a precursor that was a slurry was obtained. Next, the precursor that was a slurry was oven dried to form a precursor that was a dry powder. The precursor, which was a powder, was placed in an alumina crucible, and a pre-sintering process was performed at 800 ° C. for 2 hours in an atmosphere in which hydrogen and argon were mixed. Finally, a solid sintering process was performed on the pre-sintered powder under normal pressure at 1200 ° C. for 12 hours to obtain 213.8 g of powder. The powder was a sulfur-doped lithium lanthanum titanium oxide (LLTO) solid electrolyte powder.

[Comparative Example 1] Lithium lanthanum titanium oxide (LLTO) ... sulfur doped without lithium carbonate _{(Li 2 CO 3; Alfa Aesar} ) 18.0g, hydroxyl lanthanum (l anthanum hydroxide (La (OH ) 3); Alfa Aesar ) The same process as described in Example 1 except that 127.4 g and 105.1 g of titanium dioxide (TiO ₂ ; Evonik Industries) were mixed without adding elemental sulfur Was repeated. Finally, 212.5 g of powder was obtained. The powder was a sulfur-free lithium lanthanum titanium oxide (LLTO) solid electrolyte powder.

Lithium Ion Conductivity Test A lithium ion conductivity test was performed on the powders obtained in Example 1 and Comparative Example 1 by alternating current (AC) impedance analysis. The pre-sintered powders of Example 1 and Comparative Example 1 were compressed and molded into the shape of a tablet. The tablet was then placed in an alumina crucible to obtain tablet-shaped sulfur doped / unsulfurized lithium lanthanum titanium oxide (LLTO) solid electrolyte powder, and the solid sintering process was performed at 1200 ° C. under normal pressure. It took place for 12 hours. AC impedance analysis was performed using a tablet shaped test unit 200 with the structure shown in FIG. The tablet-shaped test unit 200 is, as shown in FIG. 2, formed of an upper cover 202, a lower cover 212, a pad 204, lithium metal 206, an isolation film 208 (including an electrolyte), and sulfur-doped tablet It was composed of lithium lanthanum titanium oxide (LLTO) solid electrolyte powder 210 that was not sulfur-doped. The results of AC impedance analysis were calculated, and the lithium ion conductivity results of Example 1 and Comparative Example 1 are shown in Table 1.

Referring to Table 1, according to the experimental results, according to the experimental results, lithium lanthanum titanium oxide (LLTO) solid electrolyte powder doped with 2.4 wt% sulfur of Example 1 was compared with lithium lanthanum titanium without sulfur doping of Comparative Example 1. Compared with the oxide (LLTO) solid electrolyte powder, the lithium ion conductivity (S / cm) at the grain boundary is from 2.92 × 10 ⁻⁵ (S / cm) to 1.0 × 10 ⁻⁴ (S Increased to / cm). The lithium ion conductivity at the grain boundary of the lithium lanthanum titanium oxide (LLTO) solid electrolyte powder doped with 2.4 wt% sulfur is the same as the original lithium lanthanum titanium oxide (LLTO) solid electrolyte powder without sulfur doping The lithium ion conductivity at the crystal grain boundary increased about 3 to 4 times. Furthermore, the total crystalline lithium ion conductivity increased from 6.4 × 10 ^-5 (S / cm) to 2.8 × 10 ^-4 (S / cm). The total lithium ion conductivity of lithium lanthanum titanium oxide (LLTO) solid electrolyte powder doped with 2.4 wt% sulfur, the total of lithium lanthanum titanium oxide (LLTO) solid electrolyte powder without the original sulfur doping It increased about 4 to 5 times with respect to lithium ion conductivity.

  In the sulfur-doped oxide solid electrolyte powder provided by the present invention, the migration rate of lithium ions is improved, and the total lithium conductivity is 4-5 times that of the original non-sulfur-doped oxide solid electrolyte powder. And significantly increased. Thus, the problem of the conventional solid electrolyte having a low lithium ion conductivity due to the grain boundary blockage was solved. Furthermore, the sulfur-doped oxide solid electrolyte powder provided in the present invention can be applied to a solid state battery, and the solid electrolyte can be used in practice.

  It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the invention. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.

DESCRIPTION OF SYMBOLS 100 Solid battery 102 Positive electrode layer 104 Negative electrode layer 106 Solid electrolyte layer 108 Positive electrode collector 110 Negative electrode collector 200 Tablet-shaped test unit 202 Upper cover 204 Pad 206 Lithium metal 208 Separation membrane 210 Tablet-shaped solid electrolyte powder 212 Lower cover

Claims (6)

A sulfur-doped lithium lanthanum titanium oxide (LLTO) solid electrolyte powder in which the amount of sulfur is 2 wt% to 3 wt% with respect to the weight of the oxide solid electrolyte powder. The sulfur-doped lithium lanthanum titanium oxide (LLTO) solid electrolyte powder according to claim 1, wherein the sulfur is elemental sulfur (S). The sulfur-doped lithium lanthanum titanium oxide (LLTO) solid electrolyte powder according to claim 1, wherein the sulfur is distributed in crystals of the oxide solid electrolyte. Positive electrode layer,
A solid battery comprising: a negative electrode layer; and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer and comprising the sulfur-doped lithium lanthanum titanium oxide (LLTO) solid electrolyte powder according to claim 1. The solid battery according to claim 4 , wherein the solid electrolyte layer further contains an adhesive or an organic solid electrolyte. The solid state battery according to claim 4 , wherein at least one of the positive electrode layer and the negative electrode layer contains the sulfur-doped lithium lanthanum titanium oxide (LLTO) solid electrolyte powder.

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